Well, I use Reptiworms, but they're essentially the same kind of larvae. My bearded dragon used to immediately charge for the dish when it was filled with Reptiworms. But after a month or so, my bearded dragon went through a phase of disinterest with them. But I found that for some reason, he preferred to eat them when they were outside of the dish. Whenever he saw one roaming on the reptile carpet of his terrarium, he instantly took an interest in them again. I also found that if I picked up the larvae individually, and then dropped them into the terrarium repeatedly (to make them seem like they're moving more, almost as if "hopping" like a cricket), my bearded dragon would start eating them.
Now he eats from the dish again, but will only come to it if I lure him towards the dish by dropping the larvae in a path. What a weird little pooper I have.
Anyway, these are just some things I've tried. I think some don't have interest merely because they don't. Others lose interest because the larvae don't move as much as what they're used to hunting (I would assume, if you've used crickets before), and sometimes it's really just the environment (I've heard that some bearded dragons have a difficult time seeing the worms in certain colors and types of dishes). But hopefully he'll pick up on them. Good luck! :]